Experimental sash units of Pinus strobus L. and Pinus resinosa Ait. wood were removed from a test fence at Ottawa, Canada after outdoor exposure of over 20 years. The units were superficially treated, prior to painting, with preservatives containing either copper naphthenate, pentachlorophenol or a combination of zinc naphthenate and pentachlorophenol. Results indicated that all treatments were effective in reducing incidence of decay. Unpainted controls were badly deteriorated. Painted controls deteriorated less, indicating that paint can provide some measure of protection. Nails were corroded to various degrees in wood treated with all preservatives except for wood treated with the zinc naphthenate-pentachlorophenol mixture. In this case nails were free from obvious corrosion and held the wood firmly. Evaluation of 20 years' observation shows that a 10-year exposure should give adequate results on the effectiveness of a preservative system.

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